Marine vessels and other structures such as platforms often include multiple engines driving electrical generators and/or mechanical systems to operate one or more primary loads such as propulsion systems, drilling apparatus and the like, and various auxiliary loads such as heating, ventilation and air conditioning (HVAC), lighting, pumps, and others. The engines can be mechanically connected to the loads or electrically connected to the loads by way of generators. In some applications, the loads of a vessel can be driven both mechanically and electrically in a hybrid arrangement.
In typical applications, the various generators, each of which is operated by an engine, are associated on one or more electrical buses and are operated to produce about the same electrical power in proportion to their rated power depending on the then-present electrical load on the bus to which the generators are connected to. For example, a particular marine vessel may have four identical engines, each engine driving a generator capable of producing about 5,000 kW. During operation, when a loading on the electrical bus consumes about 4,000 kW, each of the engine/generator sets may be operated to produce about 1,000 kW. When a load changes, all engines are operated at a higher or lower output to match the load consumption on the bus.
This type of operation may often cause the engines to operate in an inefficient operating condition, both in terms of their steady state operation and also in their transient operation. The inefficient operating may include a large fuel consumption, and may also include undesirable operating conditions in terms of various operating parameters.
Variations in the way of operating multi-engine systems in this context to improve overall system operation have been proposed in the past. For example, U.S. Patent Application Publication No. 2016/0259356 (“Converse”) describes a power system in which each of a plurality of power sources is controlled to operate in a particular zone based on the current operating mode of each power source and also based on overall load demand on the system. In particular, Converse describes a control arrangement in which the overall power of the system is apportioned among the plurality of power sources, equally or unequally, based on any number of performance goals, including fuel consumption, transient response, emissions, system wear, and the like.